Cartridge shutter actuating device in .Iadd.a Magneto optical .Iaddend.recording and/or reproducing apparatus

ABSTRACT

A device for opening a shutter of a disc cartridge along with insertion of the disc cartridge into a holder of a recording and/or reproducing apparatus for performing recording and/or reproducing operation is disclosed. The device includes at least one arm member freely rotatable about a pivot provided at one end thereof and having at the other end a first engaging portion adapted to be in engagement with the shutter substantially during insertion of the disc cartridge. A guide means or a slot extending in an oblique direction between the cartridge inserting direction and a direction in which said shutter is slided to open is provided for guiding therealong a second engaging portion of the arm member during first-step advancement of the disc cartridge into the holder from an unloaded position to a half-loaded position, thereby rotating the arm member to open the shutter due to continued engagement thereof with the first engaging portion. The pivot of the arm member is supported by a sliding member and is sliding therewith in the cartridge inserting direction during second-step advancement of the disc cartridge from the unloaded position to a full-loaded position. A spring is connected between the arm member and the holder or apparatus for biasing the arm member toward a direction opposite to the cartridge inserting direction.

This is a continuation of copending application(s) Ser. No. 07/265,212,now U.S. Pat. No. 4,899,238 filed on 10/31/88.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic recording and reproducingapparatus, and more particularly to a device equipped therewith forautomatically opening and closing a shutter of a disc cartridge used incombination with the recording and/or reproducing apparatus along withinsertion and discharge of the disc cartridge.

2. Description of the Prior Art

As a medium of magnetic or magneto optical recording and reproducing, ithas recently been known a magnetic or magneto optical disc.

In the U.S. Pat. No. 4,517,617 issued to Ohkawara, there is disclosed adisc cartridge comprising a hard jacket made from such material asplastic. The recording disc is substantially enveloped within the hardjacket for preventing damage and contamination of the disc itself and/ora recording area thereof which otherwise might occur when handling thedisc or inserting it into the recording and reproducing apparatus. Thehard jacket is provided with an aperture for insertion of a magnetichead mounted on the recording and reproducing apparatus when installedor loaded thereon. This head insertion aperture is normally closed by ashutter member slideably connected to the hard jacket, capable ofpreventing dust or fingerprints from entering through the head insertionaperture and therefore preventing contamination of the recording area ofthe disc. The shutter is provided with an access window which will allowthe magnetic head to obtain access to the recording area of the disc,when the disc cartridge is loaded into the apparatus, for performingdesired recording and/or reproducing operation.

With the system and apparatus disclosed in the above-referred U.S. Pat.No. 4,517,617 the shutter must be hand-manipulated to be laterally slidor opened before the disc cartridge is loaded into the apparatus, andafter completing desired recording and/or reproducing operation and thendischarging the disc cartridge out of the apparatus, the shutter must beclosed by the operator's hand, which is troublesome. Further,fingerprints or other foreign matter would be adhered to the recordingarea of the disc when manipulating the disc cartridge for opening orclosing the shutter.

This problem can be solved by a mechanism or device capable ofautomatically opening and closing the shutter as the disc cartridge isbeing inserted into the apparatus and discharted out of the apparatus. Atypical one of such device is disclosed in the Japanese Utility-ModelPublication Sho. 62-15895, which includes an operating lever rotatablymounted on the recording and reproducing apparatus and a cut-out notchformed at one side of the front edge of the shutter. The lever has atits one end a vertical pivot connected to the apparatus and at the otherend a leading end in engagement with the notch of the shutter, said oneend forward a direction opposite to the cartridge loading direction andthe other end forward a direction opposite to the cartridge ejectingdirection. During the cartridge loading or advancing operation, theengagement between the other end of the lever and the notch will causethe shutter to automatically open. While, in turn, the cartridge isbeing ejected away from the loaded position in the apparatus, the leveris rotated in the opposite direction due to a spring means connected tothe apparatus, as well as another spring means connected between theshutter and the hard jacket for normally biasing the shutter toward theclosed position, thereby automatically closing the shutter.

In the above-referred prior art device, the lever is arrangedsubstantially above the shutter of the disc cartridge which isfull-loaded in a holder of the magnetic recording and reproducingapparatus and there is required a considerable space for installing theshutter operating mechanism above the apparatus. In another typerecording and reproducing apparatus for use in combination with magnetooptical disc, however, as known, it will be necessary to mount a biasmagnet on the apparatus in opposition to an optical head mechanism,across the disc in the cartridge installed in the loaded position, whichbecomes difficult or practically impossible to install the shutteroperating lever substantially above the shutter as in the same manner inthe prior art device.

We have attempted that the aforementioned prior art arrangement of theshutter operating lever be modified such that the pivot is mountedrelatively in the backside of the apparatus with the engaging endoriented toward the cartridge loading direction. However, realization ofsuch arrangement has been found difficult because a relatively greatangle should be provided between the lever and the cartridge in order toactuate the shutter without a hitch, and the lever has a length in alimited range which is of necessity determined in correspondence with astroke required for opening and closing the shutter. This will beespecially difficult where the notch formed in the front edge of theshutter is arranged in close vicinity to the side face of the disccartridge, leaving only a limited space available on the apparatus formounting the pivot of the lever arranged outwardly of the side face ofthe disc cartridge.

SUMMARY OF THE INVENTION

It is therefore a principle object of the invention to provide a novelshutter actuating mechanism or device for use in combination with arecording and reproducing apparatus, capable of actuating a cartridgeshutter without a hitch, even when there is provided only a limitedspace available in the outside a cartridge receiving holder on theapparatus.

Another object of the invention is to provide a shutter actuatingmechanism which is most adaptable to a magneto optical recording andreproducing apparatus.

Still another object of the invention is to provide a shutter actuatingdevice used in combination with a magneto optical recording and/orreproducing apparatus, capable of completely opening the cartridgeshutter when a disc cartridge is advanced up to a half-loaded positionin the cartridge receiving holder, and therefore unnecessitating a shiftmechanism for shifting a bias magnet to be mounted in opposition to thedisc cartridge.

In accordance with an aspect of the invention there is provided a devicefor actuating a cartridge shutter slidably attached to a disc cartridgecontaining therein a magneto optical disc. The shutter actuating deviceis used in a magneto optical recording and/or reproducing apparatus forperforming recording and/or reproducing operation with respect to themagneto optical disc, having a holder for accommodating the disccartridge, a bias magnet secured to the holder in opposition to one sideof the disc in the disc cartridge in a full-loaded position in theholder, a base for mounting thereon an optical head in opposition to theother side of the disc in the full-loaded disc cartridge and a spindlemotor for rotating the disc in the full-loaded disc cartridge, and ashift mechanism for relatively shifting the base with respect to thedisc cartridge to make operative the optical head and the spindle motoralong with insertion of the disc cartridge into the holder. Thecartridge shutter actuating device is arranged for opening the shutteralong with insertion of the disc cartridge into the holder in adirection substantially perpendicular to the sliding direction of theshutter. The device comprises at least one arm member rotatable about apivot provided at one end thereof and having first and second engagingelements substantially at the other end thereof, the first engagingelement being engageable with a corresponding abutment formed in thecartridge shutter during insertion of the disc cartridge into theholder; first guide means extending in an oblique direction between thecartridge inserting direction and the shutter sliding direction forguiding therealong the second engaging element to thereby rotate the armmember about the pivot; supporting means for movably supporting thepivot of the arm member in the cartridge inserting direction; and springmeans for biasing the arm member toward a direction opposite to thecartridge inserting direction. The second engaging element is guided bythe first guide means to rotate the arm member up to a certainrotational angle about the pivot to thereby open the shutter due toengagement between the first engaging element and the abutment of theshutter, during insertion of the disc cartridge into the holder from anunloaded position to a half-loaded position. During succeeding insertionfrom the half-loaded position to a full-loaded position, the pivot issupported by the supporting means to move in the cartridge insertingdirection with the certain rotational angle of the second engagingelement being unchanged.

BRIED DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the invention will beapparent from the following description of a preferred embodimentthereof when read in conjunction with the accompanying drawings inwhich:

FIGS. 1, 2 and 3 are top, front and bottom views respectively, showing adisc cartridge adapted to be used for a recording and reproducingapparatus according to the invention, from which a shutter is detached;

FIG. 4 is an oblique view showing construction and arrangements on thefront and bottom of the disc cartridge, from which the shutter is alsodetached;

FIGS. 5 and 6 are top and front views respectively, showing the disccartridge which is equipped with the shutter in its closed position;

FIGS. 7, 8 and 9 are top, front and bottom views respectively, showingthe disc cartridge which is equipped with the shutter in its openedposition;

FIG. 10 is an oblique view showing construction and arrangements on thefront and bottom of the disc cartridge which is equipped with theshutter in its opened position;

FIGS. 11, 12 and 13 are a top view, a side view partly in section and afront view respectively, showing especially a main chassis, a slidingplate, a base plate and other components and parts associated therewithof a recording and reproducing apparatus embodying the invention,provided the disc cartridge is full-loaded into the apparatus, thoughthe disc cartridge itself is not shown;

FIGS. 14, 15 and 16 are a top view, a side view and a front viewrespectively, showing especially a cartridge holder, a shutter actuatingmechanism and a cartridge locking mechanism of the apparatus, providedthe disc cartridge is full-loaded into the apparatus, though the disccartridge itself is not shown;

FIGS. 17 and 18 are a top view and a side view partly in sectionrespectively, showing the base plate and a motor and an optical headmechanism mounted thereon together with the disc cartridge in thefull-loaded position;

FIGS. 19 through 22 illustrates the apparatus in the cartridge ejectedcondition, in which FIGS. 19 and 20 are top and side views showing theapparatus, exclusive of the motor and the optical head mechanism,together with the disc cartridge in an ejected position, FIGS. 21 and 22are top and side views showing the apparatus, exclusive of a slidingplate locking mechanism and the optical head mechanism, together withthe disc cartridge in the ejected position;

FIGS. 23 through 26 illustrates the apparatus in the cartridgefull-loaded condition, as in the same manner in FIGS. 19 through 22; and

FIGS. 27 through 34 are top views showing step by step how the shutteractuating mechanism according to the invention is operated along withinsertion of the disc cartridge into the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 to 4 show a disc cartridge adapted to be used with a recordingand/or reproducing apparatus according to a preferred embodiment of thisinvention. In these drawings a shutter has been removed from the disccartridge. This disc cartridge 1 comprises a disc-shaped recordingmedium (this term will be hereinlater referred to simply as "disc") 2such as magnetic disc and magneto optical disc, which is contained in asubstantially flat, box-shaped hard jacket 3 made from hard plasticmaterial, for example.

Disc 2 is particularly a magneto optical disc having recording areas onboth sides. Disc 2 is provided with a circular center opening 4surrounded by ring-like raised flanges 5 on both sides as particularlyseen in FIG. 18. Above each of outer face of disc 2, a magnetic centerplate 6 of a ferromagnetic material such as steel is supported by theraised flange 5 and extend in parallel to the disc face with apredetermined small distance therebetween. The magnetic center plate 6is provided with a circular center hole 7 for insertion of a spindle ofa motor when the disc cartridge (this term will be hereinlater referredto simply as "cartridge") 1 takes a loaded position wherein it iscompletely loaded to the recording/reproducing apparatus for performingdesired recording and/or reproducing operation.

The hard jacket 3 is assembled by joining together an upper half 3a anda lower half 3b with suitable screw means. Each of halves 3a and 3b isprovided at a center thereof with a spindle insertion aperture 9surrounded by an inwardly raised ring-like projection 10 (FIG. 18). Theprojecting depth of projection 10 is so determined as to provide adistance between the opposited two projections 10 in the hard jacket 3,as assembled, which is somewhat larger than the thickness of disc 2,whereby disc 2 is allowed to be slightly moved in the up-and-downdirection within a range restricted between the opposite two projections10. Also, disc 2 is displaceable in a horizontal direction with respectto the hard jacket 3 because there is a small clearance between theinner edges of the hard jacket 3 and the outer peripheral of disc 2. Insummary, there is provided the looseness of disc 2 fitted in the hardjacket 3 both in vertical and lateral directions. However, once thecartridge 1 is placed into the loaded condition, the verticaldisplacement of disc 2 is prevented by supporting the lower face on arotor of the motor projecting through the spindle insertion aperture 9,and the lateral displacement is restricted by the spindle 69 projectingthrough the hole 7, so that the disc 2 is maintained in a definiteposition with respect to the cartridge 1.

The hard jacket 3, as assembled, has a recess 11 for slideablyconnecting a shutter having generally a U-shaped cross-section. Therecess 11 is provided with guide means cooperated with guide pinsprojecting from the shutter for allowing lateral movement of theshutter. In this embodiment, the guide means include a rear ridge 12aextending laterally over substantially a whole width of the hard jacket3, along its rear peripheral edge, and first and second front ridges 12band 12c, splitted by a rectangular aperture 13 for disposing therecording/reproducing area 8 of the disc 2, which extend substantiallyparallel to the rear ridge 12a along the front peripheral edge of thehard jacket 3. These ridges 12a, 12b and 12c are all adapted to be comeinto sliding contact with the inner face of the shutter. A referencenumeral 14 shows a label adhered to the shutter face for use inrepresenting the recorded subjects, for example.

The cartridge 1 used in this embodiment is, as usual, equipped withwrite protection means 15 for preventing the recorded information fromaccidental or erroneous erasure. The write protection means 15 includesa piece 17 slideably received in a slot 16 formed on the upper face ofthe hard jacket 3. On the lower face of the hard jacket 3 is formed awrite protection hole 18 which is positioned between a light emittingelement and a light receiving element (both not shown) mounted in theapparatus when the cartridge 1 is in the loaded position. When theoperating piece 17 is positioned as shown in FIG. 1, the hole 18 isclosed thereby so as to interfere with light transmission between theelements, in which case the disc 2 is ready for normal recordingoperation. If, in turn, the piece 17 is manually shifted down from theposition shown in FIG. 1 to open the hole 18, which enables the lightemitting from the first element to reach the second element, no freshinformation can be recorded on the upper side of the disc 2. A similarwrite protection means is provided for the opposite, lower side of thedisc 2, which includes a write protection hole 19 (FIG. 1). Furtherdetailed description of the write protection means 15 is omitted sincethis arrangement is conventional and does not concern the materialfeatures of this invention. A reference square hole 20 is formed onopposite sides of the cartridge 1, which is used to maintain thecartridge 1 in the loaded position in a manner described later.

The cartridge 1 is of reversible type and therefore fundamentalarrangements on the lower face of the hard jacket 3 will be the same ason the upper face described before. Similar and corresponding membersand elements on the lower face are accompanied by the same numeralnumbers. However, the shutter guide means 12 is slightly different onthe upper and lower faces. More particularly, the shutter guide means 12provided on the lower face comprises a rear ridge 12d extendinglaterally with respect to the cartridge loading direction along the rearedge and adapted to be in sliding contact with the inner face of theshutter, guide grooves 12e and 12f extending parallel to the rear ridge12d along the front peripheral edge and adapted to receive guide pins(described later) projecting from the inner face of the shutter, andfirst and second ridges 12g and 12h, aligned with each other andextending along the front edges of the guide grooves 12e and 12frespectively, adapted to be in sliding contact with the inner face ofthe shutter.

Near the rear peripheral edge of the cartridge 1 there are formednotches 21 on both sides, which include inwardly inclined faces 22. Asbest shown in FIG. 2, the front edge of the cartridge 1 has plural faceat different levels. More particularly, there are a first face 22aextending along the front edge of the ridge 12b formed on the upper faceof the cartridge 1, a second face 22b, extending parallel to the firstface 22a across a groove 23, a narrow, central third face 22c, and afourth face 22d, the lowest one, connecting the ridges 12c and 12h. Thelevel difference between the first and second faces 22a and 22b willprovide a passage of an inwardly directing curved portion 28 (FIG. 10)of the shutter during the lateral sliding movement. The groove 23 formedfor passing a spnng 30 (FIG. 5) therebetween. While advancing cartridge1 in the direction shown by the arrow A in FIG. 1, first face 22a is atany time positioned ahead of fourth face 22d, which is material forautomatic shutter opening operation according to this invention, asdescribed later in detail. The width (l₁) of third face 22c iscoincident with the thickness (l₂) of disc 2 so that disc 2 can not beseen behind third face 22c in FIG. 2.

The shutter 24 of steel, aluminum, synthetic resin, etc. is slideablyattached to the hard jacket 3 as shown in FIGS. 5 to 10. Shutter 24 hason both sides access windows 25. The front ends of access windows 25 areconnected by a narrow neck 26, which is an integral part of the frontedge of the shutter 24. The width (l₃) of neck 26 is the same as thewidth (l₁) of face 22c and also as the thickness (l₂) of disc 2. Atopposite sides of the front edge of the shutter 24 there are formed acut-out notch 27 and curved portion 28, respectively.

FIGS. 5 and 6 show the shutter 24 in its closing position. Spring 30 isconnected between a fixed point on the extreme side of the front edge ofhard jacket 3 and an inwardly projecting hook 29 and extends withingroove 23, for biasing the shutter 24 toward the opposite side of thehard jacket 3 so that the shutter 24 is normally maintained in theclosing position. With the shutter 24 in the closing position, the headwindow 13 is closed by the faces of shutter 24 for protecting the discfrom accidental contamination and damage.

A pair of guide pins 31 (FIG. 9) projecting inwardly from the bottom ofshutter 24 are fitted into guide grooves 12e and 12f respectively. Withsuch guidance, by pulling the shutter 24 against the biasing force ofspring 30, shutter 24 may be laterally slided from the closing positionto another, opening position shown in FIGS. 7 to 10. In this openingposition, guide pins 31 are positioned at extreme ends of guide grooves12e and 12f respectively. With the cartridge 1 in the closing position,the spindle insertion aperture 9 and head window 13 formed on the hardjacket 3 are both completely opened via the access window 25 of shutter24.

The recording/reproducing apparatus used in connection with thecartridge 1 as described above will now be described with reference toFIGS. 11 to 18. The apparatus embodying the invention is symmetric withrespect to the center line extending in the cartridge loading direction.In the following description, in main, only one of symmetricallyarranged members or elements will be described and only one side of theapparatus is shown in drawings.

Specifically referring to FIGS. 11 to 13, a main chassis 40 generallyforms the outer panel of the apparatus. The rightmost (seen in FIGS. 11and 12) ends of main chassis 40 extend upwardly to form inwardlyprojecting base mounts 41 to which required circuit plate (not shown) issecured. The open top of main chassis 40 is substantially covered by aholder bottom plate (FIGS. 14 to 16) secured thereto. The center ofholder bottom plate 42 is cut out to form a wide, U-shaped access window43 enabling the optical head mechanism and spindle to have access to thedisc 2 when the cartridge 1 is in the loaded position. The cut-outextends upwardly and turned as L-shaped to form a bias magnet attachment44 to which a bias magnet 55 comprising a coil 54 coiled around anE-shaped core 53 is mounted as shown in FIG. 15. The bias magnet 55 willbe opposed to the recording/reproducing area 8 of disc 2 to create amagnetic field, in the loaded position of cartridge 1.

The holder bottom plate 42 is provided symmetrically with respect to thecenter line extending in the cartridge loading direction with each onepair of first, second and third slots 45, 46 and 47. As best shown inFIG. 14, the first slot 45 extends straight along the peripheral edge ofthe holder bottom plate 42 from the leftmost end 45a to the right. Thesecond slot 46 is formed inside of the first slot 45 and includes arectilinear portion 48 extending substantially parallel to the firstslot 45 between the rightmost end 48a and the leftmost end 48b and acrescent-shaped portion 49 formed integral with the rectilinear portion48. The crescent-shaped portion 49 is formed by an arcuate edge 49a anda first and second bowstring-shaped edges 49b and 49c connected by astep 49d. The center of arc 49a will be a pivot pin 114 when a slidingmember 113 is positioned in the leftmost end 45a, and the radius of arc49a will substantially correspond to the distance between pins 114, and117 of an arm 115 which will be described later in detail. The thirdslot 47 is formed between the first and second slots 45 and 46 andincludes a straight portion 47a extending in the cartridge loadingdirection and an enlarged portion 47b formed integral with the leftmostend of the rectilinear portion 47a.

The side peripheries of the holder bottom plate 42 are bent upwardly andthen inwardly to form integrally side walls 50 and top flanges 51. Thus,a cartridge holder is constituted by the holder bottom plate 42, sidewalls 50 and top flanges 51 to provide a cartridge inserting/dischargingport 52 as well as a space for receiving and supporting the cartridge.To the side wall 50 is attached inside an attachment plate 50a made ofsynthetic resin, for example, for smoothening insertion and discharge ofcartridge 1.

With the apparatus described, when cartridge 1 is completely receivedwithin the holder to occupy the loaded position, at the same time orimmediately thereafter, drive mechanism retractably mounted within theapparatus is shifted from the lower, stand-by position to the upper,operative position wherein necessary positional relationship is achievedwith respect to the loaded cartridge 1 or disc 2. Specifically referringagain to FIGS. 11 to 13, a base 58 is formed integrally by a centerplate 58a to which the drive mechanism including a motor 56 and anoptical head mechanism (FIGS. 17 and 18) is secured, side plates 58bstanding from the side peripheries of center plate 58a, and flanges 58cextending outwardly from the top portions of side panels 58b, Betweenthe rear-end portions of side panels 58b and main frame 40 are connectedvia pivots 59 which allows the base 58 to be pivotted between thestand-by position and the operative position. FIGS. 11 to 13, 17 and 18show the base 58 in the operative position in which the upper face ofthe base mount 58a will be level and therefore a spindle 69 of motor 56is set upright, just across the cartridge 1 in the loaded position.

On the flange 58c of base 58 there is formed means for maintaining thecartridge 1 in the loaded position. This positioning means comprises apair of first reference pins 60 planted on flange 58c at substantially acenter thereof, a pair of second reference pins 61 near the cartridgeinserting/discharging port 52 and a pair of leaf springs 70 (FIG. 15)installed on the holder top plates 51. The first reference pins 60 areadapted to mount thereon the leading end portion of cartridge 1 in theloaded position, which is cooperated with the leaf springs 70 providedfor exerting a downward pressure, through openings 51a, onto thecartridge, to restrict vertical displacement or movement of thecartridge. Second reference pins 61 are adapted to be received withinthe corresponding reference holes 20 of cartridge 1 for preventinglateral displacement or movement of the cartridge. Second reference pinsare equipped with elastomeric O-ring 62 whereupon the holder bottomplate 42 will lay down.

The spindle motor 56 is, for example, a three-phase motor consisting ofsix coils 63 and a magnet 64₁, polorized in eight sections. The coils 63is coiled around a base portion 66 on a substrate 65. The magnet 64₁ issecured to the underside of a rotor 67 which is rotatable together withspindle 69 penetrating through the base portion 66 via bearing means 68.

Besides the positioning of cartridge 1 in the loaded position which isachieved by means of reference pins 60 and 61 and leaf springs 70,definite positioning of disc 2 within the cartridge 1 should also becontemplated as it is received in the cartridge with some looseness bothin vertical and lateral directions. In this embodiment, verticaldisplacement or movement of disc 2 is prevented in such manner that thetop of rotor 67 is fitted into the spindle insertion aperture 9 to comeinto contact with the lower face of disc 2, and lateral positioning orcentering of disc within the loaded cartridge is established by thespindle 69 penetrating through the hole 7 of disc 2. In the loadedposition of cartridge 1, there will be provided a tendency that a magnet64₂ secured to rotor 67 attracts the magnetic center plate 6 of disc 2.The spindle motor 56 used in this embodiment is of conventional flattype and can therefore be replaced by another suitable one.

As best shown in FIGS. 17 and 18, the optical head mechanism has anoptical source 71 including as known a laser diode, a polarizer plate, abeam splitter, etc. from which a laser beam is projected to a reflectivemirror (not shown) in the cartridge loading direction, when the baseplate 58 is in the operative position. The reflection is directedupright toward an object lens 73 so that a spot of the laser beam isconcentrated to the recording/reproducing area 8 of disc 2 in the loadedcartridge 1. The objective lens 73, as well as a focussing coil 74 and atracking coil 75, are secured to a support 77 which is rotatable about avertical shaft 76 and vertically slideable along the shaft 76. Above thebase plate 58 there is attached an optical head base 78 for mountingthereon yokes 79 and a magnet 80, which constitute a magnetic circuitboth for focussing and tracking operation. A linear guide 81 is securedto the optical head base 78 and adapted to be in engagement within aguide rail 82 attached to the base plate 58. By means of a linear motorhaving a coil 83 and a magnet 84, the linear guide 81 is driven in thecartridge loading direction along the guide rail 82 to actuate theoptical head base 78 theretogether.

Again reference should be made to FIGS. 11 and 13. Between a pin 85protruding outwardly from the flange 58c of the base plate 58 and anengaging nail 86 formed at opposite sides of the basement of mainchassis 40 is connected a spring 87 to normally bias the base plate 58to rotate in the clockwise direction as viewed in FIG. 12. The pin 85 isequipped with a freely rotatable guide roller 88 which has a materialmeaning in the movement of a sliding plate.

A sliding plate 89 is integrally formed by a bottom 89a, an ejectingbutton 89b extending from the fore end of the bottom 89a, at least apart thereof being always protruded to the outside through an aperture(not shown) formed in the front panel of main chassis 40, and a pair ofside walls 89c extending upwardly from the side edges of the bottom 89a.Slots 91 are formed in the bottom 89a for slideably receiving pins 90planted on the bottom of main chassis 40, and slots 93 are formed in theside walls 89c for slideably accomodating pins 92 projecting inwardlyfrom the side walls of main chassis 40. A part of the bottom 89a is cutout to form a projection 94 for engaging one end of a spring 95 havingthe other end connected to the pin 90, so that the sliding plate 89 isnormally biased to move toward the ejection, namely to the left in FIGS.11 and 12. The sliding plate 89 is slideable in the cartridgeloading/ejecting direction under guidance of pins 90 and 92 engagedwithin slots 91 and 93, respectively.

A middle portion of the side wall 89c of sliding plate 89 is cut out assubstantially triangular-shape to form a slot 96 (FIGS. 20 and 24) forguiding the guide roller 88 rotatably provided around pin 85 of baseplate flange 58c along with movement of the sliding plate 89, wherebythe base plate 58 can be shifted between the stand-by position and theoperative postion. Near the rear end of the slot 96 is formed a verticalcut-out 97 adapted to engage one end of a sliding plate locking arm(FIG. 20).

The sliding plate locking arm 98 is substantially L-shaped and supportedrotatably about a pin 99 secured inwardly to the side wall of mainchassis 40. The locking arm 98 has at its one end an outwardlyprojecting pin 100 engageable with the cut-out 97, and the otherinwardly directing extension 101. The arm 98 is normally biased torotate in the counter clockwise direction (as viewed in FIG. 12) bymeans of a spring 102 coiled around the pin 99.

Specifically referring to FIGS. 14 to 16, behind the access window 43formed on the holder bottom plate 42, there are planted a pair of pins103a and 103b and a pair of link arms 104a and 104b rotatable about thepins 103a and 103b, respectively. The inner ends of the link arms 104aand 104b are rotatably connected to an interlocking pin 105, which isconnected or secured to nothing but these arms, so that these arms willbe moved in complete unison with each other. More particularly,supposing one of the arms 104a is rotated about the pivot 103a in somedegree of rotational angle, the other arm 104b is Followed to rotateabout the pivot 103b in the opposite direction in the same degree. Tothe outer end of each arm is secured a push pin 106 extending downwardlybelow the holder bottom plate 42 through the third slot 47 to beengageable with the extension 101 of sliding plate locking arm 98.

Means for locking the cartridge 1 is also provided. A lever 108 operatedfor this purpose is rotatably supported by a pivot axis 107 projectingdown from the holder bottom plate 42 near the cartridgeinserting/discharging port 52. The locking lever 108 has a rod-likeportion 108a mounted beneath the holder bottom plate 42, the leading endof which extends upwardly to form a projection 108b adapted to enter thecartridge receiving space encircled by the holder. The projection 108bwill come into engagement with the notch 21 formed on the side ofcartridge 1 so as to maintain cartridge 1 in the loaded position. To therear end of the rod-like portion 108a is press-fit a downwardlyprojecting pin 109. A spring 110 is connected between the pin 109 and aprojection formed on the holder bottom plate 42 and coiled around thepivot 107, thereby normally biasing the locking lever 108 to rotate inthe counter clockwise direction as seen in FIGS. 19 and 23. Whencartridge 1 is carried in the loaded position, at which time the baseplate 58 is maintained in the operative position with the sliding plate89 being set free from the locking mechanism, as particularly shown inFIG. 23, the pin 109 is in contact with the outer face of the side wall89c of sliding plate 89, causing the locking lever 108 to rotated in theclockwise direction against the biasing force of spring 110 so that theprojection 108b is brought into engagement with the notch 21 formaintaining the loaded position of cartridge 1. When, in turn, cartridge1 leaves out of the loaded position and thus the base plate 58 isshifted down to the stand-by position with the sliding plate 59 beinglocked, as shown in FIG. 19, the sliding plate 89 has been shifted tothe right further from the position of FIG. 23, the pin 109 is now incontact with the face 111 (FIG. 19) extending inward of the side wall89c, whereby the lever 108 is slightly rotated in the counter clockwisedirection to release the engagement between the projection 108b andnotch 21. During ejecting or discharging operation of cartridge 1, thelocking lever 108 is retracted for ensuring smooth movement of cartridge1.

Shutter opening mechanism which concerns the subject matter of thepresent invention will now be described with reference to FIGS. 14 to16. In these drawings, the shutter opening mechanism is shown as thecartridge 1 having been carried into the loaded position, thoughcartridge itself is not shown. This mechanism includes a sliding member113 having a pair of rotatable guide rollers 112a and 112b which areadapted to fit into the first slot 45 formed on the holder bottom plate42 to make the sliding member 113 slideable therealong. The slidingmember 113 is equipped with a supplemental guide roller 116 between theguide rollers 112a and 112b, which will provide resilient contact withthe inner wall of the holder side wall 50 for smoothening the slidingmovement. To the leading end of the sliding member 113 is press fit apin 114. The sliding member 113 has an inwardly extending flap 113aadapted to be in sliding contact with the apex of the arm 115.

In the shutter opening mechanism there is also mounted a triangular arm115 having one apex pivoted to the pin 114. The other two apexes of arm115 has downwardly projecting pins 117 and 118 adapted to be fitted intothe second slot 46 and third slot 47 of the holder bottom plate 42,respectively. The apex including the pin 118 is engageable with theextended flap 113a to restrict the rotation of arm 115. The apexincluding the pin 117 is integrally formed with a pin 119. The arm 115is normally biased to move toward the ejection by means of a spring 120having one end connected to the pin 118 and the other end supported by aprojection formed at the fore edge of the holder bottom plate 42.

Now, explanation will be given about the operation of the apparatushaving the aforesaid construction.

FIGS. 19 to 24 show the condition created by inserting the leadingportion of cartridge 1 into the cartridge receiving space through theport 52 until the notch 27 comes into engagement with the pin 119planted on the one extreme end of the arm 115. In this condition, theapparatus will be defined as in an "ejected position". In this ejectedposition, as particularly seen from FIGS. 19 and 20, the cartridgelocking lever 108 remains in its retracted position in which the pin 109is received in the recess 110 to retreat the projection 108 from thecartridge, so that the cartridge loading operation will not beinterfered. The base plate 58 is in the stand-by position, namely thedrive mechanism including motor 56 and optical head mechanism 57 is inwhole retracted below the holder bottom plate 42, having no partprotruding into the cartridge receiving space. The pin 100 of thesliding plate locking arm 98 is fitted into the recess 97 so that thesliding plate 89 is retained in a locked fashion in the rightmostposition, against the spring 95. The pin 85 outwardly projecting fromthe flange 58c is received deep in the corner of the guide slot 96. Thepush pin 106 of the link arm 104 is in touch with the end 101 of arm 98.

When cartridge 1 is advanced from the ejected position, through a"half-loaded position" to be described later, a "full-loaded position"will be attained as shown in FIGS. 23 to 26. The apparatus is ready forexpected recording and/or reproducing operation in this full-loadedcondition.

Along with the cartridge loading operation, the shutter opening arm 113is first operated to open the shutter 24. More particularly, whencartridge 1 is completely loaded into the holder to be installed in theloaded position, one of the arm 115, the lower one in FIG. 23, isoperated to move forward due to contact with the leading face ofcartridge 1, whereby the arm 104b is rotated in the counter clockwisedirection, which causes at the same time the other arm 104a to rotate inthe opposite direction. As a result, by virtue of contact between thepin 106 of arm 104b (104a) and the extension 101 of the sliding platelocking arm 98, arm 98 is rotated in the clockwise, direction to releasethe locking condition of sliding plate 89, which will then start movingto the left by means of spring 95. Along with the sliding movement ofthe plate 89, at first, the cartridge locking lever 108 is rotated inthe clockwise direction (in FIG. 23) to maintain the cartridge in theloaded position through engagement between the projection 108b and thenotch 21. Then, the base plate 58 is rotated about the shaft 59 in theclockwise direction (in FIG. 24) and shifted from the retracted positionto the upper operative position, while guiding the pin 85 along theinclined edge of the guide slot 96.

Such a series of operation, including shutter opening operation,cartridge locking operation and base plate shifting operation, will bedescribed in detail with special reference to FIGS. 27 to 34.

FIG. 27 illustrates the position of various components associated withthe holder bottom plates 42 when the apparatus is in the ejectedposition shown in FIGS. 19 to 22. As having been described, the ejectedposition is created when the cartridge 1 is loaded so that the pin 119(119A) planted on one end of the shutter opening arm 115 (115A) isbrought into engagement with the notch 27 formed at one end of the frontedge of cartridge 1. At this time, the arm 115A is drawn by the spring120A toward the port 52, whereby the pin 117A remains in the leftmostend of the slot 46A and the pin 118A in the leftmost end of the enlargedportion 47b of the slot 47A. The sliding attachment 113A is also pulledtoward the port 52 by the pin 114A so that the guide roller 112a is alsopositioned in the leftmost end 45a of the slot 45A. Here, it should bereminded that the fore edge of cartridge 1 has plural faces atdifference levels in the cartridge loading direction and that the face22d including the notch 27 is at any time somewhat behind-hand of theface 22a. Accordingly, in the ejected position, the pin 119B of anotherarm 115B has been already pushed by the leading face 22a, and the pin117B has been moved from the leftmost end of the slot 46B to the rightand now is ashore on the first straight edge 49b. The pin 118B has beencaused to move within the enlarged portion 47b of the slot 47B. In thisconnection, attention should be paid to the fact that while the shutteropening operation is governed by the first arm 115A, the position of thesecond arm 115B will be at any time moved ahead of the arm 115A due tocontact with the leading face 22a of cartridge 1.

While cartridge 1 is further advanced from the ejected position of FIG.27, arm 115A is being pivotted in the counter clockwise direction aboutthe pin 114A. In this course of movement, the shutter 24 is caused to belaterally slid or opened through engagement between pin 119A and notch27 of cartridge 1. Along with further advancement of the cartridge, theposition shown in FIG. 28 and then in FIG. 29 will be obtained.

In FIG. 29, the pin 119B of the second arm 115B, which had been operatedin contact with the leading face 22a of cartridge 1, has run on to thecurved portion 28 of cartridge 1. At this time, the pin 117B of secondarm 115B is just on the step 49d formed between the first and secondbowstring-like extending edges 49b and 49c. The step 49d will providefor a retreat of the pin 117B, thereby ensuring smooth rotation of thearm 115B along with further advancement of cartridge 1, which otherwisemight be struck as the curved portion 28 is inclined substantially inparallel with the extending edge 49b. Thereafter, the pin 119B will runashore on the front edge of the shutter 1 and then be running in contacttherewith.

Along with further advancement of cartridge 1, the apparatus positionwill vary from that shown in FIGS. 30 and 31 to that of FIG. 32 in whichthe pin 117A of first arm 115A has reached the connecting point 48bbetween the crescent-shaped portion 49A and the rectilinear portion 48Aof the slot 46A. While the pin 117A is being shifted in contact with thefirst extending edge 49b, the retreating step 49d and the secondextending edge 49c, in due order, from the ejected position in FIG. 27to the position in FIG. 32 which will be referred to as a "half-loadedposition" in the following description, the pivot pin 114A must beslightly moved for leaving a predetermined distance from the pin 117A.This will be achieved by such arrangement that the slider 113A isallowed to be reciprocated along the slot 45A. The pin 118A tremblesirregularly within the enlarged portion 47b of the slot 47A.

In FIG. .[.40.]..Iadd.32.Iaddend., the shutter 24 has completely openedso that the spindle opening 9 and the head opening 13 on the cartridge 1are entirely exposed through the shutter access window 25. With theshutter 24 completely opened, the narrowed portion 22c and 26 provide arecess for the bias magnet 55. During the further advancement ofcartridge 1, disc 1 is free from contact with the bias magnet 55 whichis secured to the apparatus at a level higher only by approximately 1 mmthan the disc face when the cartridge 1 is loaded in the holder.

Along with further advancement of cartridge 1 from the half-loadedposition shown in FIG. 32, due to continued engagement between the pin119A and the notch 27, the pins 117A and 118A are moving into therectilinear portion 48A of the second slot 46A and the rectilinearportion 47a of the third slot 47A, respectively, thus shifting the firstarm 115A to the right. The slider 113A accompanied by the pivot pin 114Ais also moved to the right along the first slot 45A together with thearm 115A. The arm 115A is slided in the cartridge loading direction withits orientation kept unchanged by virtue of the extended flap 113a ofthe slider 113A which remains in contact with the apex of the arm 115A.The apparatus is thus advanced to the position of FIG. 34 through FIG.33.

As described before, the second arm 115B will always go ahead of thefirst arm 115A. In FIG. 34, though the pin 118A of first arm 115A isstill in the course of sliding movement along the slot 47A, the pin 118Bof second arm 117B has already reached the rightmost end of the slot47B, which push forward the leading end of the second link 104b. Whilethe leading end of the first link 104a is not directly actuated by thepin 118A, it is operated in synchronism with the second link 104b by theaforesaid interlocking mechanism. With the synchronized butopposite-directing motion of the first and second links lima and 104b,the push pins 106A and 106B projecting down from the leading ends of thelinks 104a and 104b respectively will be moved in the cartridge loadingdirection (to the right), which in turn push the extention 101 of thesliding plate locking arm 98 so that the arm 98 is rotated in theclockwise direction as best viewed in FIG. 20. The pin 100 is escapedfrom the recess 97 of the sliding plate 89, thereby releasing thelocking condition of sliding plate 89, which results in that slidingplate 89 is moved to the ejection by means of the spring 95. The slot 94formed in the bottom 89a receiving the pin 90 and the slot 93 in theside 89c receiving the pin 92 will provide guidance for sliding movementof the plate 89. As the sliding plate 89 moves in this manner, the baseplate 58, which has been retracted in the stand-by position with the pin85 received deep in the guide slot 96 of the sliding plate 89, willrotate in the clockwise direction to ascend to the operative position asshown in FIGS. 11 to 13 capable of performing desired recording and/orreproducing operation.

The sliding movement of the plate 89 will also govern the cartridgelocking operation. More particularly, while the sliding plate 89 remainsin the locked condition, as clearly shown in FIG. 19, the pin 109 of thecartridge locking lever 108 is received within a recess formed by theinner contact face 111 of the sliding plate 89, whereby the leading end108b go outwardly away from the side wall of cartridge 1. When thesliding plate 89 starts sliding, the pin 109 is now in contact with thecartridge side wall so that the lever 108 is about to rotate in theclockwise direction but is prevented from doing so until the projection108b enter the notch 21 formed near the rear end of cartridge 1. Thus,cartridge 1 can be supported in a definite position by the locking lever108 which is operated along with the sliding movement of the plate 89.

It should be noted that the base plate ascending operation is performedwith a slight time lag later than the cartridge locking operation. Moreparticularly, at the time when cartridge 1 is locked in position, thepin 85 still stays halfway on the inclined edge of the slot 96 andtherefore the base plate 58 has not reached the operative position.Still further movement of the sliding plate 89 will be enough to ascendthe base plate 58 to the operative position as specifically shown inFIGS. 23 and 25.

As having been described, with the illustrated apparatus, the shutteropening operation is completed in the half-loaded stage. Then, aftercompletely loading the cartridge 1 in the cartridge receiving space, thesliding plate 89 is released out of the locked condition to startsliding, whereupon the cartridge locking mechanism is made operative andimmediately thereafter the base plate 58 reaches the operative position.Thus, there is provided the loaded position as shown in FIGS. 23 to 26in which desired recording and/or reproducing operation can beperformed. In the loaded position, a portion of the ejecting button 89bof the sliding plate 89 is protruded to the outside of the apparatus soas to provide for the cartridge ejecting operation to be described next.

After performing desired recording and/or reproducing operation,cartridge is ejected from the loaded position. This cartridge ejectingoperation is carried out by operating by hand the button 89b to therebyadvance the plate 89 toward the cartridge loading direction against thespring 95, which will actuate the base plate shifting mechanism and thecartridge locking mechanism in a fashion substantially reversed from inthe aforementioned spring-back movement. More particularly, the pin 85is guided along the inclined edge of the slot 96 to shift the base plate58 down finally to the stand-by position against the spring 87. Furtheradvancement of the sliding plate 89 will release engagement between theprojection 108b and the notch 21 to set the cartridge 1 free from thelocking mechanism. The sliding plate 89 is advanced until the pin 100 isreceived in the recess 97 for locking the plate 89 in the inoperativeposition. With the cartridge locking mechanism released, the arm 115 ispulled back by the spring 120, thereby ejecting and dischargingcartridge 1 through the port 52. In the course of movement of the arm115, the shutter 24 is closed at the half-loaded stage.

During the cartridge ejecting operation, the arm 115 will be moved fromthe full-loaded position in FIG. 34 to the half-loaded position in FIG.32 in the reversed manner from during the cartridge loading operation.After passing through the half-loaded position in FIG. 32, however, thearm 115 will not take position shown in FIGS. 31 to 28 but is directlyreturned to the ejected position in FIG. 27 by the biasing force of thespring 120 which rotates the arms 115A and 115B about the pivot pins114A and 114B, remained in the leftmost position as shown, in theopposite directions with the pins 117A and 117B rotated along thearcuate edges 49a and 49a, respectively.

Although in the foregoing description use of one side of the cartridge 1is contemplated, the apparatus of the illustrated embodiment is adaptedto be used for the cartridge 1 of reversible type. The shutter openingmechanism is completely symmetric with respect to the center lineextending in the cartridge loading direction. If the cartridge, asturned upside down, is loaded into the apparatus, the notch 27 willaccomodate the pin 119B of the second arm 115B and the first arm 115Awill at any time be ahead of the second arm 115B.

Although only a specific embodiment of the invention has been describedin detail with reference to the accompanying drawings, it is to beunderstood that the invention is not limited to the illustratedembodiment and various changes and modifications may be made withoutdeparting from the scope and spirit of the invention as defined in theappended claims. For example, the function and operation of the pins 117and 119 can be achieved by a single pin.

What is claimed is:
 1. .[.In a.]. .Iadd.A .Iaddend.magneto opticalrecording and/or reproducing apparatus for performing recording and/orreproducing operations with respect to a magneto optical disc containedin a disc cartridge, .[.having.]. .Iadd.which comprises: .Iaddend.aholder for accommodating the disc cartridge, a bias magnet secured tothe holder in opposition to .[.one.]. .Iadd.a first .Iaddend.side of thedisc in the disc cartridge in a full-loaded .Iadd.cartridge.Iaddend.position in the holder, a base .[.for mounting.]. .Iadd.havingmounted .Iaddend.thereon an optical head in opposition to .[.the otherside of.]. .Iadd.the bias magnet across .Iaddend.the disc in thefull-loaded .[.disc.]. cartridge.[., and.]. .Iadd.position and having.Iaddend.a spindle motor .[.for rotating.]. .Iadd.rotatably engaging.Iaddend.the disc in the full-loaded .[.disc.]. cartridge .[.and.]..Iadd.position, .Iaddend. a shift mechanism .[.for relatively shiftingthe base with respect to the disc cartridge to make operative theoptical head and the spindle motor along with insertion of the disccartridge into the holder,.]. .Iadd.disposed between the base and theholder and operably shifting said base with respect to said holderbetween an entry orientation maximizing a distance from the bias magnetto the optical head with the disc cartridge in a unloaded cartridgeposition outside said holder, and an operate orientation minimizing adistance from the bias magnet to the optical head when the disccartridge is in the full-loaded cartridge position, and .Iaddend. acartridge shutter actuating device for opening a laterally slidableshutter of the disc cartridge along with insertion thereof into.[.the.]. .Iadd.said .Iaddend.holder in a direction substantiallyperpendicular to the sliding direction of the cartridge shutter,.[.which comprises: at least one arm member rotatable about a pivotprovided at one end thereof and having first and second engagingelements substantially at the other end thereof and having first andsecond engaging elements substantially at the other end thereof, saidfirst engaging element being engageable with a corresponding abutmentformed in the cartridge shutter during insertion of the disc cartridgeinto said holder; first guide means extending in an oblique directionbetween the cartridge inserting direction and the shutter slidingdirection for guiding therealong said second engaging element to therebyrotate said arm member about said pivot; supporting means for movablysupporting said pivot of said arm member in the cartridge insertingdirection; and spring means for biasing said arm member toward adirection opposite to the cartridge inserting direction; said secondengaging portion being guided by said first guide means to rotate saidarm member up to a certain rotational angle about said pivot to therebyopen the cartridge shutter due to engagement between said first engagingelement and said abutment of the cartridge shutter, during insertion ofthe disc cartridge into said holder from an unloaded position to ahalf-loaded position, and during succeeding insertion from thehalf-loaded position to a full-loaded position, said pivot beingsupported by said supporting means to move in the cartridge insertingdirection said with certain rotational angle of said second engagingelement being unchanged.]. .Iadd.said cartridge shutter actuating devicehaving means for opening the cartridge shutter during insertion of thedisc cartridge from the unloaded cartridge position wherein the shutteris in a closed shutter position to a half-loaded cartridge position witha leading edge proximate to said bias magnet and with the shutter in afully opened shutter position completely exposing an opening in thecartridge in a half-loaded cartridge position, and means for maintainingthe cartridge shutter in the fully opened shutter position duringsucceeding insertion of the disc cartridge from the half-loadedcartridge position to the full-loaded cartridge position.Iaddend.. .[.2. The apparatus according to claim 1 wherein said supporting meanscomprises a sliding member guided along a second guide means extendingsubstantially in the cartridge inserting direction along the sideperiphery of said holder..]..[.3. The apparatus according to claim 2wherein said first guide means comprises a bowstring edge of acrescent-shaped slot having an arc substantially corresponding to an arcdescribed by said second engaging element when said arm member isrotating about said pivot supported by said sliding member positioned inone extreme end of said second guide means..]..[.4. The apparatusaccording to claim 3 wherein said crescent-shaped slot further extendsin the cartridge inserting direction to form a rectilinear slot portionfor allowing said second engaging element to move therealong during thesucceeding insertion of the disc cartridge from the half-loaded positionto the full-loaded position..]..[.5. The apparatus according to claim 2wherein said sliding member is provided at both ends thereof guiderollers rotatably fitted into said second guide means..]..[.6. In amagneto optical recording and/or reproducing apparatus for performingrecording and/or reproducing operation with respect to a magneto opticaldisc contained in a disc cartridge, having a main chassis, a holderfixedly connected to the main chassis for accommodating the disc to oneside of the disc in the disc cartridge in a full-loaded position in theholder, a base connected to the main chassis for mounting thereon anoptical head in opposition to the other side of the disc in thefull-loaded disc cartridge and a spindle motor for rotating the disc inthe full-loaded disc cartridge, and a shift mechanism for relativelyshifting the base with respect to the disc cartridge to make operativethe optical head and the spindle motor along with insertion of the disccartridge into the holder,a cartridge shutter actuating device mountedto said holder for opening a laterally slidable shutter of the disccartridge along with insertion thereof into the holder in a directionsubstantially perpendicular to the sliding direction of the cartridgeshutter, which comprises: at least one arm member rotatable about apivot provided at one end thereof and having first and second engagingelements substantially at the other end thereof, said first engagingelement being engageable with a corresponding abutment formed in thecartridge shutter during insertion of the disc cartridge into saidholder; first guide means extending in an oblique direction between thecartridge inserting direction and the shutter sliding direction forguiding therealong said second engaging element to thereby rotate saidarm member about said pivot; supporting means for movably supportingsaid pivot of said arm member in the cartridge inserting direction; andspring means for biasing said arm member toward a direction opposite tothe cartridge inserting direction; said second engaging element beingguided by said first guide means to rotate said arm member up to acertain rotational angle about said pivot to thereby open the cartridgeshutter due to engagement between said first engaging element and saidabutment of the cartridge shutter, during insertion of the disccartridge into said hold from an unloaded position to a half-loadedposition, and during succeeding insertion from the half-loaded positionto a full-loaded position, said pivot being supported by said supportingmeans to move in the cartridge inserting direction with said certainrotational angle of said second engaging element beingunchanged..]..[.7. The apparatus according to claim 6 wherein saidsupporting means comprises a sliding member guided along a second guidemeans extending substantially in the cartridge inserting direction alongthe side periphery of said holder..]..[.8. The apparatus according toclaim 7 wherein said first guide means comprises a bowstring edge of acrescent-shaped slot having an arc substantially corresponding to an arcdescribed by said second engaging element when said arm member isrotating about said pivot supported by said sliding member positioned inone extreme end of said second guide means..]..[.9. The apparatusaccording to claim 8 wherein said crescent-shaped slot further extendsin the cartridge inserting direction to form a rectilinear slot portionfor allowing said second engaging element to move therealong during thesucceeding insertion of the disc cartridge form the half-loaded positionto the full-loaded position..]..[.10. The apparatus according to claim 6wherein said sliding member is provided at both ends thereof guiderollers rotatably fitted into said second guide means..]..[.11. In amagneto optical recording and/or reproducing apparatus for performingrecording and/or reproducing operation with respect to a magneto opticaldisc contained in a disc cartridge, having a holder for accommodatingthe disc cartridge, a bias magnet secured to the holder in opposition toone side of the disc in the disc cartridge in a full-loaded position inthe holder, a base for mounting thereon an optical head in opposition tothe other side of the disc in the full-loaded disc cartridge and aspindle motor for rotating the disc in the full-loaded disc cartridge,and shift mechanism for relatively shifting the base with respect to thedisc cartridge to make operative the optical head and the spindle motoralong with insertion of the disc cartridge into the holder,a cartridgeshutter actuating device mounted to said holder for opening a laterallyslidable shutter of the disc cartridge along with insertion thereof intothe holder in a direction substantially perpendicular to the slidingdirection of the cartridge shutter, which comprises: at least one armmember rotatable about a pivot provided at one end thereof and havingfirst and second engaging elements substantially at the other endthereof, said first engaging element being engageable with acorresponding abutment formed in the cartridge shutter during insertionof the disc cartridge into said holder, said pivot being movable in thecartridge inserting direction; first guide means extending in an obliquedirection between the cartridge inserting direction and the shuttersliding direction for guiding therealong said second engaging element tothereby rotate said arm member about said pivot; and spring means forbiasing said arm member toward a direction opposite to the cartridgeinserting direction; said second engaging element being guided by saidfirst guide means to rotate said arm member up to a certain rotationalangle about said pivot to thereby open the cartridge shutter during toengagement between said first engaging element and said abutment of thecartridge shutter, during insertion of the disc cartridge into saidholder from an unloaded position to a half-loaded position, and duringsucceeding insertion from the half-loaded position to a full-loadedposition, said pivot being moved in the cartridge inserting directionwith said certain rotational angle of said second engaging element beingunchanged..]..[.12. The apparatus according to claim 11 wherein saidfirst guide means comprises a bowstring edge of a crescent-shaped slothaving an arc substantially corresponding to an arc described by saidsecond engaging element when said arm member is rotating about saidpivot supported by said sliding member positioned in one extreme end ofsaid second guide means..]..[.13. The apparatus according to claim 12wherein said crescent-shaped slot further extends in the cartridgeinserting direction to form a rectilinear slot portion of allowing saidsecond engaging element to move therealong during the succeedinginsertion of the disc cartridge from the half-loaded position to thefull-loaded position..]..Iadd.14. The apparatus according to claim 1wherein said means for opening the cartridge shutter comprises:at leastone arm member rotatable about a pivot provided at one end thereof andhaving first and second engagement elements substantially at the otherend thereof, said first engaging element being engageable with acorresponding abutment formed in the cartridge shutter during insertionof the disc cartridge into said holder; and first guide means extendingin an oblique direction between the cartridge inserting direction andthe shutter sliding direction for guiding therealong said secondengaging element to thereby rotate said arm member about said pivot;said second engaging element being guided by said first guide means torotate said arm member up to a certain rotational angle about said pivotto thereby open the cartridge shutter due to engagement between saidfirst engaging element and said abutment of the cartridge shutter,during insertion of the disc cartridge into said holder from saidunloaded cartridge position to said half-loaded cartridge position; andwherein said means for maintaining the cartridge shutter comprises:supporting means for movable supporting said pivot of said arm member inthe cartridge inserting direction, said pivot being supported by saidsupporting means to more in the cartridge inserting direction with saidcertain rotational angle of said second engaging element beingunchanged, during insert of the disc cartridge from the said half-loadedcartridge position to said full-loaded cartridgeposition..Iaddend..Iadd.15. The apparatus according to claim 14 whereinsaid supporting means comprises a sliding member guided along a secondguide means extending substantially in the cartridge inserting directionalong the side periphery of said holder..Iaddend..Iadd.16. The apparatusaccording to claim 15 wherein said first guide means comprises abowstring edge of a crescent-shaped slot having an arc substantiallycorresponding to an arc described by said second engaging element whensaid arm member is rotating about said pivot supported by said slidingmember positioned in one extreme end of said second guidemeans..Iaddend..Iadd.17. The apparatus according to claim 16 whereinsaid crescent-shaped slot further extends in the cartridge insertingdirection to form a rectilinear slot portion for allowing said secondengaging element to move therealong during the succeeding insertion ofthe disc cartridge from the half-loaded cartridge position to thefull-loaded position..Iaddend..Iadd.18. The apparatus according to claim1, wherein said bias magnet is secured to said holder at a level higherby approximately 1 mm than said one side of the said disc when said disccartridge is loaded in said full-loaded cartridgeposition..Iaddend..Iadd.19. The apparatus according to claim 1, whereinsaid bias magnet comprises an E-shaped core and a coil coiled aroundsaid E-shaped core..Iaddend..Iadd.20. A magneto optical recording and/orreproducing apparatus for performing recording and/or reproducingoperation with respect to a magneto optical disc contained in a disccartridge, which comprises:a holder for accommodating the disccartridge, a bias magnet secured to the holder in opposition to a firstside of the disc in the disc cartridge in a full-loaded cartridgeposition in the holder, an optical head in opposition to a second sideof the disc across the disc from the bias magnetic in the full-loadedcartridge position, a spindle motor on the second side of the dischaving a turntable to rotate the disc in the full-loaded cartridgeposition, a shift mechanism connected to the turn table and the opticalhead and operably shifting said optical head and said turntable tooperating orientation in response to insertion of the disc cartridgeinto the holder, a cartridge shutter actuating device mounted to theholder for opening a laterally slidable shutter of the disc cartridge inconnection with insertion thereof into the holder from a closed shutterposition to a fully opened shutter position completely exposing anopening in the cartridge in a half loaded cartridge position with aleading edge of the cartridge being proximate to said bias magnet, andmeans for maintaining the cartridge shutter in the fully opened shutterposition during succeeding insertion of the disc cartridge from thehalf-loaded cartridge position to the full-loaded cartridgeposition..Iaddend..Iadd.21. The apparatus according to claim 20, whereinsaid bias magnet is secured to said holder at a level higher byapproximately 1 mm than said one side of the said disc when said disccartridge is loaded in said full-loaded cartridgeposition..Iaddend..Iadd.22. The apparatus according to claim 20, whereinsaid bias magnet comprises an E-shaped core and a coil coiled aroundsaid E-shaped core..Iaddend..Iadd.23. A magneto optical recording and/orreproducing apparatus for performing recording and/or reproducingoperations with respect to a magneto optical disc contained in a disccartridge, which comprises:a holder for accommodating the disccartridge, a bias magnet mounted fixedly with respect to said holder inopposition to a first side of the disc in the disc cartridge in afull-loaded cartridge position in said holder, said bias magnet defininga half-loaded cartridge position of the disc cartridge at a point in thedirection of insertion of the disc cartridge where a front edge of thedisc cartridge is proximate to but has not yet reached said bias magnet,.Iaddend. an optical head mounted in opposition to a second side of thedisc in the full-loaded for disc cartridge and positioned for recordingand/or reproducing the disc in the full-loaded disc cartridge, and acartridge shutter actuating device mounted to the holder and opening alaterally slidable shutter of the disc cartridge in connection withinsertion thereof into said holder from a closed shutter position in anunloaded cartridge position wherein the cartridge is outside the holderto a fully opened shutter position completely exposing an opening in thecartridge in the half-loaded cartridge position.